Water table lowering
The water table lowering is the main threat to the habitat conservation. It is due to several reasons and it become more evident year after year.
Some causes are anthropic, like the lowland hydraulic draining and the increased agricultural, industrial and civil water taking; others are natural, like the rain decreasing in Friuli in the past ten years.
The lowered water table creates unsuitable conditions for the alkaline fen typical plants, as that makes them less competitive than the wet meadow species and causes peat mineralization, which increases the soil nutrients and favours more eutrophic species.
Lack of management
The water table lowering is getting worse by the habitat lack of management. In the ’60s and ’70s lots of little zootechnical farms still survived so, alkaline fens were regularly mowed - generally once a year.
Private estates have not been mowed for decades and presently, laws forbid periodic fires, which once contributed to maintain habitats clean and open.
As a result, vegetation changes fast and few competitive species prevail, weeding out the rarest species that need light, space and water.
Some woody species, especially shrubs, such as Frangula alnus and Salix cinerea, start to grow after some years without any mowing or fire and, in a short time, those changes will become irreversible.
The Friuli alkaline fens characteristics and the presence of typical plants are due to the peculiarity of groundwater. It fills – all the year long – the peaty strata which lie directly on gravelly and pebbly layers.
The water is alkaline and calcium rich but it is poor in nutrients, like nitrogen and phosphorus, which causes a highly oligotrophic habitat.
The fen closeness to high-intensive cultivations, poplar plantations and even little groves could cause nitrogen and phosphorus increasing. This, through the run-off, can cause the loss of whole sites ofoligotrophic endemic species.
In the past decade, the medium raininess has decreased, both in the project area and in the mountains, where the water comes from. In addition, almost every year there are drought periods often longer than two months.
Together with frequent high temperatures, those events completely dry up the alkaline fens, producing eutrophication and an organic matter mineralization, so that hygrophilous species disappear and the growth of new population is hindered.
Excessive habitats fragmentation
The natural habitat fragments have a very limited extension (2-20 hectares each) and they arenot much resilient to negative physical or chemical phenomena. Furthermore, they are separated by insurmountable ecological barriers for endangered species populations.
The small dimensions of the populations of lots of endemic and/or community interesting species are reducing the habitats genetic diversity and their capacity to react to environmental stress.